When finally completed and put into production, oil and gas wells located beneath the ocean or on remote platforms or other inaccessible locations are most often connected together at a common control center, and a series of flow control valves, known as chokes, are installed in the main flow line of each well to control the rate of material flow therefrom. It is desirable to provide for remote regulation of flow from each individual well by supplying each choke valve with a separate actuator capable of opening and closing the particular choke valve upon command from a remote operator.
The existence and use of such actuators is well known in the valve control art, however actuators used in subsea or other inaccessible locations for the control of producing oil or gas wells must meet particularly exacting standards. Specifically, the actuator for a subsea choke must be able to readily withstand the hostile undersea environment, which may include physical abuse, corrosive conditions, and little or no maintenance. Moreover, it is essential that the actuator be capable of selectively positioning and returning the choke to any one of a number of setpoints upon command in order to optimize the rate of production from the control well.
It is therefore an object of the actuator according to the present invention to positively rotate an elongated member, valve stem, or the like in a stepwise fashion upon the command of a remote operator.
It is a further object of the actuator according to the present invention that said stepwise motion be uniformly incremental and repeatable.
It is a still further object of the actuator according to the present invention to provide a rugged, streamlined means for rotatably positioning said elongated member, valve stem or the like.